The present invention relates to the field of surface treatments of polymer substrates, which are widely used in very many industries, especially the packaging and thermal insulation industries, or for the manufacture of insulating electrical compounds.
Nevertheless, these materials often have surface properties which make them difficult to use in conversion processes such as printing or bonding, in which processes the wetting of the substrate and its adhesion to a coating (ink, adhesive, varnish, etc.) are absolutely essential: this is because their low wettability, resulting from their structure, makes it very difficult for example to apply inks or adhesives to such surfaces.
Many types of surface treatment (preparation) of polymer substrates have therefore been developed on an industrial scale for improving their properties. These surface treatments are used by polymer film producers and by subsequent converters (printing of packaging films, manufacture of electrical capacitors, etc.).
Among the methods most widely used for carrying out these surface treatment operations are in particular liquid-phase methods.
Aside the fact that these liquid-phase methods unquestionably pose problems as regards the environmental protection standards which are becoming increasingly strict, it should also be pointed out that the application of these liquid-phase methods proves to be very tricky and difficult to control.
In this context, a second category of polymer surface treatment methods has made its appearance, which methods are termed “dry methods”.
In this category, mention may be made of the example of flame brushing treatments, which have been used for a long time in this industry, but the significant thermal effect of which makes them not easily compatible with thin substrates (films or sheets).